Facial nerve schwannoma of the tympanic segment with geniculate ganglion involvement: Diagnostic and therapeutic challenges

Abstract

Facial nerve schwannoma is a rare benign tumor arising from Schwann cells of the facial nerve, most commonly involving the geniculate ganglion and intratemporal segments, and often presenting with nonspecific clinical features that may delay diagnosis. We report the case of a 35-year-old woman presenting with progressive left-sided facial nerve palsy evolving over 15 months, ultimately classified as House-Brackmann grade VI. High-resolution computed tomography and magnetic resonance imaging revealed a well-defined lesion centered on the tympanic segment of the facial nerve with extension to the geniculate ganglion, showing characteristic enhancement without vascular flow voids. A transcanal endoscopic biopsy confirmed the diagnosis of schwannoma with positive S100 and SOX10 immunostaining. Given the advanced facial nerve dysfunction, a staged management strategy including delayed hypoglossal-facial nerve anastomosis was adopted. This case highlights the importance of early radiological evaluation in atypical facial nerve palsy and emphasizes that management should be individualized based on preoperative facial nerve function, which remains the main prognostic factor.